Latest progress on tribological properties of industrial materials (original) (raw)
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Tribological coatings for lubrication over multiple thermal cycles
Surface and Coatings Technology, 2009
Nanocomposite materials demonstrating multiple temperature-adaptive mechanisms including diffusion, oxidation and/or catalysis mechanisms to yield low friction coefficients of b0.2 from room temperature to 700°C were combined with diffusion barrier layers in coatings with different architectures (e.g., layer thicknesses, number of layers, etc.) to examine adaptation of contact surface chemistry and morphology over multiple thermal cycles. Multilayered coatings consisting of ceramic-metal nanocomposite adaptive lubricant layers separated by diffusion barriers allowed adaptation to occur only upon exposure of the lubricant layer by wear, which resulted in prolonged wear life at static and cycled temperatures. It was also observed that a relationship between the number of adaptive lubricant layers and the number of thermal cycles existed, where one thermal cycle consumed two adaptive lubricant layers. The thickness of the adaptive coating layers was also important because diffusion-and oxidation-based adaptation in these particular coatings required a minimum volume of solid lubricant material. The surface roughness of the adaptive coating materials played a significant role in their performance within multilayered coatings, where rough coatings (N 100 nm R a ) failed after relatively few sliding cycles. The utility and application of adaptive coatings materials providing lubrication over multiple thermal cycles is discussed.
Effect of metallic-coating properties on the tribology of coated and oil-lubricated ceramics
1994
Friction and wear behavior was determined for zirconia ceramics lubricated with solid coatings (Ag, Au, and Nb) deposited by ion-beam-assisted-deposition (IBAD) techniques, and a polyol-ester-based synthetic oil. Although the use of soft Ag and Au coatings as solid lubricants in conjunction with the synthetic oil significantly reduced the friction and wear under boundary lubrication at temperatures up to 250°C, these films had poor durability. In contrast,the Nb coating was more durable (in terms of chemical reactivity and adhesion during the tribo-tests) than were the Ag or Au films. However, the friction and wear behavior of the Nb-coated zirconia was poorer than that of the ceramics coated with Ag or Au.
Lubricants, 2014
The role of surface protective additives becomes vital when operating conditions become severe and moving components operate in a boundary lubrication regime. After protecting film is slowly removed by rubbing, it can regenerate through the tribochemical reaction of the additives at the contact. However, there are limitations about the regeneration of the protecting film when additives are totally consumed. On the other hand, there are a lot of hard coatings to protect the steel surface from wear. These can enable the functioning of tribological systems, even in adverse lubrication conditions. However, hard coatings usually make the friction coefficient higher, because of their high interfacial shear strength. Amongst hard coatings, diamond-like carbon (DLC) is widely used, because of its relatively low friction and superior wear resistance. In practice, conventional lubricants that are essentially formulated for a steel/steel surface are still used for lubricating machine component surfaces provided with protective coatings, such as DLCs, despite the fact that the surface properties of coatings are quite different from those of steel. It is therefore important that the design of additive molecules and their interaction with coatings should be reconsidered. The main aim of this paper is to discuss the DLC and the additive combination that enable tribofilm formation and effective lubrication of tribological systems.
Friction, Lubrication, and Wear Technology
Friction, Lubrication, and Wear Technology, 2017
Volume 18 addresses friction and wear from a systems perspective, while providing a detailed understanding of why it occurs and how to control it. It explains the basic theory of friction and wear, and offers valuable insight on the forces, mechanisms, and interactions that are involved. It examines common wear scenarios, including wear by particles or fluids, rolling-contact wear, sliding wear, impact wear, and both chemical and environmentally assisted wear. It also covers operational wear, addressing several cases, including tool and die wear, bearing wear, engine wear, turbine wear, pump wear, and seal wear. In addition, the volume provides information on lubricants and lubrication, coatings, surface treatments and modifications, and the tribology of irons and steels, cobalt-base alloys, titanium, aluminum alloys and composites, cemented carbides, ceramics, polymers, and polymer composites. It also introduces the topic of condition monitoring, addressing wear particle analysis, ...
Application of lubricant is a problem in many cases, apart from external lubrication; it is always being useful if the material itself has self-lubricating properties. Such kind of materials are GCI & PTFE+Graphite composites. In these, Graphite flakes acts as solid lubricant & when load is applied, these layers slide over another & provide lubricat ion. PTFE+Graphite is well known for its self-lubricating properties and widely emp loyed in applications, where d ry lubrication & good thermal stability are needed. Primary aim of this work is to study & compare t ribological properties of proposed self-lubricat ing materials. Tests are conducted on the POD apparatus using GCI disc and pin & PTFE+Graphite p in & AISI 1045 Steel disc specimens under different conditions. Later, linear Regression models are developed using input and output variables for both GCI Pin on GCI disc and PTFE filled with Graphite Pin on AISI 1040 Steel disc. Validation of the proposed mathematical equation wa s done by comparing experimental and predicted values of the experimentation and in all cases percentage error was found in between 0-6%. ANOVA was also performed on the experimental results to assess the conformity of the suggested mathematical model with 99% confidence levels.
Friction and wear of solid lubricant films deposited by different types of burnishing
Wear, 2007
Solid lubricant films based on MoS 2 and WS 2 are widely used for dry air friction and aerospace applications. Different plasma deposition methods are widely used for formation of solid lubricant films on the contact surfaces. One of the simple methods of solid lubricant film deposition is cloth burnishing. The aim of this work is to develop new simple methods for burnishing of steel surfaces providing improved the tribological properties of solid lubricant films. For this cause the solid lubricant particles were burnished by the loading system of balls. MoS 2 as well as some binders were used for formation of lubricant layer. In order to improve the consolidation of particles in the layer, external excitation of loading system has been used. The friction coefficient and the longevity of solid lubricant film were assessed using ball-on-flat and pin-on-disk devices. The effect of burnished films on their tribological properties is discussed.
Tribological study of thin films coatings on parts subjected to friction and wear Doctoral thesis
2022
This work is a tribological study that tend to give technical solution of the oil and gas valves that suffer from surface failures; through coatings and thin films using different processes: thermal spraying, Plasma Immersion Ion Implantation (PIII) nitriding and Physical Vapour Deposition (PVD). Thermal spraying and post spray vacuum annealing give massive coatings with high hardness (13.9 GPa) and corrosion resistance (0.069 mpy). PIII nitriding increase the hardness of the coating surface (16.4 GPa) and the W-Ti-N thin film deposited by PVD improve the tribological behaviour of the obtained multilayer system (hardness of 22.3 GPa, friction coefficient of 0.14 and a wear rate of 7.55∙10-8 mm3/N∙m).
Tribological behavior of Al-based self-lubricating composites
Composite Interfaces, 2016
Al based self-lubricating hybrid composites containing SiC as the hard phase and MoS2 as the solid lubricant were synthesized by using stir casting route. Dry sliding wear and friction characteristics of the composites have been examined at sliding speed of 1 m/s on a pin-on-disc tribometer under different normal loads of 9.8N, 14.7N, 19.6N, 24.5N. Both friction and wear rates were found to reduce with addition of MoS2, however, bonding between the matrix and reinforcements was not good. Hence, Mg was added to improve the wettability and this resulted in improved mechanical as well as tribological performance.
Wear, 2017
The performance of coatings for tribological applications is strongly associated with substrate properties and the presence of lubricants between the contacting faces. In this study, plasma nitriding followed by the application of a hydrogenated Diamond-like Carbon (DLC) film (a-C:H) was coated onto grey cast iron (GCI) substrates using a single thermal cycle. Four distinct reciprocating cylinder-plane configurations (horizontal cylinder sliding without rolling against a plane) were used: DLC coated plane on a GCI cylinder, a DLC coated cylinder vs. a GCI plane, a DLC coated cylinder vs. a DLC coated plane and an uncoated cylinder GCI against an uncoated plane GCI. These configurations were tested in dry conditions and using low viscosity oil (ISO5) lubricated reciprocating sliding tests. The respective friction coefficients and wear rates were measured. The wear tracks were analyzed using white light interferometry (WLI) to evaluate the surface topography and wear rates. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and micro Raman spectroscopy (RS) were carried out to identify the wear mechanisms. For dry tests, wear debris on the contact and DLC surfaces favour the formation of tribolayers that define the wear rates. Furthermore, regardless of the horizontal cylinder surface (coated or uncoated), the presence of DLC on the plane surface increases the dry friction coefficient. For lubricated tests, the tribolayers that formed on the metallic surfaces played a key role in governing the wear rate.